[Ifeffit] Increase in uncertainty of Eo and fitting mismatch

[Bruce Ravel]

Your data range is quite short and the data are rather attenuated
compared to a conventional EXAFS measurement.  Beyond that I cannot
really understand your narrative compared to the content of the
project file you attached.  Can you do a sensible analysis of a copper 
foil measured at a conventional beamline?

Your project file is from a version of Artemis that is over 7 years
old.  I can't and won't provide any further support for users of such an 
old version.

B



On 03/10/2015 12:11 PM, Raj kumar wrote:
> Dear All,
>
> Recently, I recorded Copper foil EXAFS as a reference in (Dispersive
> EXAFS) transmission mode at Soleil, Paris. For understanding the data
> quality (of my sample), i started fitting copper EXAFS through Artemis.
> After the DATA extraction, i fitted copper in Artemis and found a shift
> in energy. For this reason, i have modeled with and without corrected
> Copper EXAFS in Artemis. Initially, i started with first shell and
> progressed to three shell fit through step by step. During the course of
> fitting, some of the following troubles have been faced. Please help me
> to rectify it.
>
> For first shell fit: Everything goes well and converged to reasonable
> physical values of copper foil. Whereas for*further increment in copper
> shells* leads to *increase in Debye-waller factor for all three shells*
> and *increase in uncertainty value of E0 than the actual value*.
>
> Moreover, i have noticed that the (increase of shells in the fit) *not
> only changes the physical parameters and also modifies the Fourier
> transform*.  The inference are the following: A shift in first and third
> shell of Cu-Cu are observed, respectively, *to larger and shorter
> distance than the experimental spectrum* with diminished second shell
> amplitude.
>
> Although Copper foil EXAFS is standard and well known sample, i am stuck
> with fitting. Please help me to overcome these problems. For your
> reference, project file of Copper file is attached with this email.
>
> Regards.
> Raj
>
>
>
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-- 
  Bruce Ravel  ------------------------------------ bravel at bnl.gov

  National Institute of Standards and Technology
  Synchrotron Science Group at NSLS-II
  Building 535A
  Upton NY, 11973

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